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Figure. 5.3.5 - 42. Simplified function block diagram of the Idir> function.
Measured input
The function block uses analog current measurement values. The user can select the monitored
magnitude to be equal either to RMS values, to TRMS values, or to peak-to-peak values. TRMS mode
uses values from the whole harmonic spectrum of 32 components. Peak-to-peak mode picks
measurement values directly from the samples. A -20 ms averaged value of the selected magnitude is
used for pre-fault data registering.
The fault current angle is based on the comparison between the positive sequence voltage
U
1
and the
positive sequence current
I
1
. If the positive sequence voltage is not available (three line-to-line voltages
but no
U
0
), the voltage angle is based on a faulty phase line-to-line voltage. If the voltage drops below
1 V in the secondary side during a fault, the voltage memory is used for 0.5 seconds. After that the
reference angle of voltage is forced to 0°.
Table. 5.3.5 - 81. Measurement inputs of the Idir> function.
Signal
Description
Time base
IL1RMS
RMS measurement of phase L1 (A) current
5ms
IL2RMS
RMS measurement of phase L2 (B) current
5ms
IL3RMS
RMS measurement of phase L3 (C) current
5ms
IL1TRMS
TRMS measurement of phase L1 (A) current
5ms
IL2TRMS
TRMS measurement of phase L2 (B) current
5ms
IL3TRMS
TRMS measurement of phase L3 (C) current
5ms
IL1PP
Peak-to-peak measurement of phase L1 (A) current
5ms
IL2PP
Peak-to-peak measurement of phase L2 (B) current
5ms
IL3PP
Peak-to-peak measurement of phase L3 (C) current
5ms
U
1
RMS
RMS measurement of voltage U
1
/V
5ms
U
2
RMS
RMS measurement of voltage U
2
/V
5ms
U
3
RMS
RMS measurement of voltage U
3
/V
5ms
U
4
RMS
RMS measurement of voltage U
4
/V
5ms
A
AQ
Q-C255
-C255
Instruction manual
Version: 2.06
92
© Arcteq Relays Ltd
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